Advanced Configuration and Power Interface Specification

Definition of Terms
2
Definition of Terms
This specification uses a particular set of terminology, defined in this section. This section has three
parts:
General ACPI terms are defined and presented alphabetically.
The ACPI global system states (working, sleeping, soft off, and mechanical off) are defined. Global
system states apply to the entire system, and are visible to the user.
The ACPI device power states are defined. Device power states are states of particular devices; as
such, they are generally not visible to the user. For example, some devices may be in the off state
even though the system as a whole is in the working state. Device states apply to any device on any
bus.
2.1 General ACPI Terminology
Advanced Configuration and Power Interface (ACPI)
As defined in this document, ACPI is a method for describing hardware interfaces in
terms abstract enough to allow flexible and innovative hardware implementations and
concrete enough to allow shrink-wrap OS code to use such hardware interfaces.
ACPI Hardware
Computer hardware with the features necessary to support OSPM and with the
interfaces to those features described using the Description Tables as specified by this
document.
ACPI Namespace
A hierarchical tree structure in OS-controlled memory that contains named objects.
These objects may be data objects, control method objects, bus/device package
objects, and so on. The OS dynamically changes the contents of the namespace at runtime
by loading and/or unloading definition blocks from the ACPI Tables that reside
in the ACPI system firmware. All the information in the ACPI Namespace comes
from the Differentiated System Description Table (DSDT), which contains the
Differentiated Definition Block, and one or more other definition blocks.
ACPI Machine Language (AML)
Pseudo-code for a virtual machine supported by an ACPI-compatible OS and in which
ACPI control methods and objects are written. The AML encoding definition is
provided in section 19, “ACPI Machine Language (AML) Specification.”
Advanced Programmable Interrupt Controller (APIC)
An interrupt controller architecture commonly found on Intel Architecture-based 32-
bit PC systems. The APIC architecture supports multiprocessor interrupt management
(with symmetric interrupt distribution across all processors), multiple I/O subsystem
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